FIELD OF THE INVENTION
The present invention relates generally to radiotelephonic communication systems such as a terrestrial-cellular communication system or a satellite-cellular communication system. Particularly, the present invention relates to circuitry, and an associated methodology, for initiating communications with a user terminal, i.e., a radiotelephone, operable in such a radiotelephonic communication system. More particularly, the present invention relates to circuitry, and an associated methodology, for the improved reception and correlation of an acknowledgment signal transmitted by the user terminal in the radiotelephonic communication system.
To initiate communications with the user terminal, a paging signal is transmitted from a broadcast station to the user terminal to page the user terminal. When the user terminal receives the paging signal, the user terminal returns an acknowledgment signal acknowledging reception of the paging signal. The user terminal might be operating in an environment in which the acknowledgment signal might be significantly attenuated. The possibility of significant levels of attenuation which prevent adequate communication of the acknowledgment signal is particularly problematical when the user terminal is operable in a satellite-cellular communication system, and the acknowledgment signal must be transmitted over a significant distance to a satellite-based transceiver.
To facilitate communication of the acknowledgment signal, the "margin" of the acknowledgment signal is increased to distinguish better the acknowledgment signal over background noise. As the power level of the user terminal is limited and cannot normally be increased, the margin of the acknowledgment signal cannot be increased by increasing its power level. Instead, by encoding the acknowledgment signal according to a selected encoding technique, the margin of the acknowledgment signal is increased and reception improved. In this manner, communication of the acknowledgment signal is facilitated. By acknowledging reception of the paging signal, repeated transmission of paging signals to the user terminal, once the radio telephone has received the paging signal, is avoided. And, if an acknowledgment signal is not detected, the paging signal is retransmitted at a higher margin level, such as by increasing the power level of the paging signal or by encoding the paging signal according to a different encoding scheme or a combination thereof. The result of the repetitive paging is, of course, a drain on satellite and other system resources.